1. Field of the Invention
The present invention is directed generally to the field of debris removal, and specifically to an apparatus that is capable of retrieving a wide variety of litter and refuse from any type of surface, such as a road surface, while the apparatus is in continuous forward motion.
2. Description of Related Art
A common type of litter collecting device includes a single pick up roller or drum rotatably supported on a frame which is movable over the ground. In its simplest form, the device is simply a sweeper, an example of which is disclosed in U.S. Pat. No. 3,771,189, issued to Horton et al. Resilient fingers project from the rollers to entrap, or at least redistribute, litter during rotary contact with the ground. The entrapped litter is then lifted from the ground by the fingers as the roller or drum rotates.
If the device is to be used to actually entrap and store the litter, a smaller, elevated brush roller downstream from the pick up roller can be employed to remove and transfer trapped litter from the fingers for discharge into a trash bin carried by the frame. An example of such a device is disclosed in U.S. Pat. No. 3,923,101, issued to Donahue.
The major problem encountered by such roadbed engaging devices is brush or finger wear. The brush must have some resilience in order to avoid breaking when repeatedly encountering the unyielding road surface. Thus, numerous researchers have addressed the problem of designing a strong wear resistant brush capable of some deflection, the proper amount of deflection often being a somewhat poorly defined parameter. For example, U.S. Pat. No. 3,649,984, issued to Kershaw et al., discloses a brush element having a protruding steel core surrounded by a rubber sheath. The steel core limits maximum deflection while adding a substantial weight penalty. Hence, the roadbed sweeper with which such bristles are used is required to have a substantial power source as well as a relatively rugged transmission. A similar rubber element reinforced with a series of spring steel plates is disclosed in U.S. Pat. No. 4,484,373, issued to Price. The use of bundles of bare wire brush elements without any sort of coating is disclosed in U.S. Pat. No. 4,662,044, issued to Kayabara.
An attempt to utilize a more resilient brush or finger is disclosed in U.S. Pat. No. 2,286,650, which uses a brush element formed of pure gum rubber. Additional flexibility is obtained by cutting a series of lateral grooves into the exterior of the brush element. However, the brush disclosed is far too fragile to withstand repeated contact with a road surface, and is in fact intended for use with a poultry plucking machine. A somewhat stronger brush is disclosed in U.S. Pat. No. 4,480,350, issued to White, which uses a substantially identical brush element as found in the '650 disclosure, with the addition of internally molded fiber reinforcing elements. U.S. Pat. No. 4,367,564 discloses a stiffer brush element having a rounded leading edge and reinforced by an internally molded, stranded, fibrous material.
All of the above mentioned brush elements suffer from being excessively heavy and requiring the combining of multiple materials into a specific composite structure. Further, each of the aforementioned brushes must be individually mounted by threading into a receptacle or being individually secured by separate threaded fasteners. Such mounting arrangements are a major source of dissatisfaction in a litter collecting environment, since debris tends to foul such fastening arrangements and tools are required to replace each individual brush. An attempt to simplify the mounting of the brush is disclosed in U.S. Pat. No. 5,160,187, issued to Drumm, in which a continuous brush is mounted to a continuous clip which is then inserted into a groove residing on the rotating drum. However, a method of adapting such an arrangement to a series of discrete finger elements is not disclosed.
While the above devices are somewhat effective to remove certain types and quantities of litter scattered over relatively large areas, the rotating pick up fingers often fail to initially engage or retain entrapped litter for subsequent removal by the elevated brush roller. Consequently, substantial quantities of litter remain on the ground. Additionally, substantial quantities of litter lifted by the fingers are often ejected back onto the ground by the rotating brush roller.
Another type of litter collecting apparatus utilizes a tandem pair of identical, oppositely rotating rollers, as disclosed in U.S. Pat. No. 2,916,753, issued to Redpath et al. Each roller supports many radially extending fingers which engage the ground, and which also intermesh in a gear like fashion with the fingers of the adjacent roller. This type of prior art apparatus tends to lift greater quantities of litter from the ground than the single roller/elevated brush arrangement discussed above, since litter not grasped by the front roller fingers is usually lifted by the rear roller fingers.
In order to transfer litter to a downstream conveyor for discharge into a rear trash bin, Redpath et al. uses plural elevated, finger projecting rollers meshing with front and rear finger projecting, ground level rollers. The elevated and ground level rollers convey litter downstream along an arcuate transfer path above the ground level rollers. Difficulties are encountered, however, in maintaining precise control over transfer of litter entrapped between the fingers of the ground level rollers. Specifically, there is a tendency for the elevated rollers to redeposit entrapped litter onto the ground since the fingers cannot maintain positive control over all types of litter so as to insure movement to the conveyor residing along the same transfer path. Also, whereas the rollers yield to uneven terrain, the equipment is complex and cumbersome, increasing production and maintenance costs.
In all of these machines, the transfer of the collected litter from the collector to the storage bin involves a number of discrete handling steps in which the litter goes from one location to another between the ground and the storage bin. However, each time that a piece of litter must be handled by a separate piece or structure in the machine there exists an opportunity for the overall collecting efficiency of the machine to be reduced. For example, when a transfer of litter between two relatively moving machine elements is required, it is always possible that flexible types of litter such as cardboard cartons or paper wrappers can become jammed between the two elements. Rather than being transferred from one element to the other, the litter may be returned to the ground or require stoppage of the machine to clear the obstruction.
In another type of entrainment action, collected litter may be allowed to freely drop from one type of handling apparatus into another. For example, it may fall from a collecting roller into a trap area where it is picked up by a subsequent handling device. In such situations, it is entirely possible that litter such as a glass bottle or the like may break as it falls into the trap area, allowing the smaller pieces to drop through spaces in the machine and return to the ground.
U.S. Pat. No. 3,993,141, issued to Donahue, employs a relatively simple collecting concept that does not involve numerous handling steps in transferring the litter from the collecting device to the storage bin. However, the basic collecting device itself is too simple in concept, comprising a series of relatively rigid rods mounted on a shaft and adapted to picking up only certain types of litter or litter of certain sizes that is capable of being wedged between the rods.
U.S. Pat. No. 4,550,465, issued to Chrisley, utilizes a plurality of flexible fingers to collect litter, the fingers being subject to wear, thus reducing their effectiveness. The fingers in such prior art machines are difficult to replace, and their circular cross section tends to deflect rather than entrain at least some portion of the debris.
U.S. Pat. No. 5,247,717, issued to Smith, also utilizes flexible fingers arranged on opposed conveyors to lift debris entrained by a pair of ground engaging rollers. The fingers are intermeshed so as to increase the probability of entraining and transferring a high percentage of the litter, and the multiple conveyor scheme reduces the horizontal length of the litter collecting apparatus, leaving a greater length available for use as a collection hopper for a vehicle of a given size. However, the intermeshed fingers require a controlled timing sequence among the various rollers that prevents rapid variations in conveyor and collector speeds. Further, certain types of litter, such as blankets or carpeting, tend to become entangled in the intermeshed fingers which define a relatively tortuous path for the entrained litter. The intermeshing of the fingers and the spacing of the opposed conveyors impose a finite limit on the size of the debris which may be transported through the space in between the conveyors. Although the collection bin is potentially enlarged, there is no mechanism to insure that substantially the entire volume of the bin will be filled before the proximity of the collected debris to the conveyors will preclude further debris entrainment. Finally, the length of the vehicle is such that the collection bin is necessarily behind the rearmost wheels of the vehicle, resulting in wide center of gravity variations and undesirable low frequency undamped resonant oscillations of the entire vehicle at certain, unpredictable speeds.
U.S. Pat. No. 4,434,011, issued to Moore, discloses a litter collection device in which a series of fingers engage the ground and transfer entrained litter to a single conveyor. Rotating discs are interposed between each row of fingers to strip entrained debris and direct it to the conveyor. The ground engagement feature of this device promotes a high rate of finger wear, while the rotating discs add substantial mechanical complexity and power transmission requirements.
In summary, previously developed litter collecting machines have not solved the problem of collecting the wide variety of litter that is commonly found on surfaces such as, for example, highways. In particular, the previous devices have been subject to incomplete litter collection, jamming and fouling of collection elements, poor utilization of the available collection bin volume, limitations on the size and shape of the debris which can be entrained and an inability to operate while in motion at any substantial forward velocity. The lack of reliability of prior art debris pick up devices has caused most public safety departments with responsibility for high speed limited access highways to routinely block traffic in all lanes in anticipation of debris removal by a stationary vehicle assisted by pedestrian personnel. This practice is inherently dangerous, slow and labor intensive.